a) Field of the Invention
The present invention relates to a musical tone synthesizing apparatus and method, and more particularly to an apparatus and method for synthesizing a musical tone by a feedback loop system having a delay element and a filter.
b) Description of the Related Art
Recently, a sound source of an electronic musical instrument for synthesizing musical tones, called a physical model of a natural musical instrument, has been proposed in which the natural mechanism of generating sounds is replaced by an electronic circuit. The common characteristic feature of such physical models is to synthesize musical tones by exciting an oscillation in a loop circuit including a delay element and a filter, a delay caused by the delay element corresponding to the period of musical tones to be synthesized and an attenuation caused by the filter corresponding to the reflection loss of sound waves.
In such a physical model of a piano, for example, a Filter and a delay are connected in a loop to simulate a string of a piano. A strike on a string by a hammer is also replaced by an electronic circuit or signal. Namely, an excitation signal is injected to the loop to synthesize musical tones of the piano. In another physical model of a piano, a wave simulating an impact wave generated upon striking a string is stored in a wave memory. The wave is read from the memory to inject it into the loop and synthesize musical tones of the piano.
Conventional physical models has on one hand the advantage that during the rising and decay processes of oscillation, a power of expression similar to that of a natural musical instrument can be obtained and the manner of change in musical tones is natural, and has on the other hand the disadvantage that it is difficult to synthesize musical tones exactly the same as those generated by a natural musical instrument.
However, an absolute physical model cannot be formed practically. Physical phenomena can be replaced by electronic circuits only as approximate alternatives. Physical phenomena which have not been solved to date, are also present. If electronic circuits simulating every details of a physical phenomenon are designed without any approximation, this system becomes enormously large.
Even in the case where a wave simulating an impulse wave is stored and read, this physical model of a string is not complete. Selecting a suitable impulse wave has relied upon a trial and error basis.